Marine protein sources are often utilized in feeds because they are an excellent source of essential amino acids, fatty acids, vitamins and minerals, and because they generally enhance palatability. Alternative ingredients can be used in the feed industry in place of fish meal. For this reason, many studies have been conducted on the replacement of expensive marine proteins with lower cost ingredients. Considerable attention has been devoted to the replacement of fish meal with plant protein; lemnae, as a natural protein source, has a better array of essential amino acids than most other vegetable proteins and resembles animal protein more closely. Newly harvested lemnae contain up to 43% protein by dry weight and can be used without further processing as a complete feed for fish. Compared with most other plants, lemnae leaves contain little fiber (5% in dry matter for cultivated plants) and little to essentially no indigestible material even for monogastric animals. This contrasts with the compositions of many crops such as soy beans, rice, and maize, approximately 50% of whose biomass comprises residues high in fiber and low in digestibility.
Lemna is a genus of free-floating aquatic plant from the duckweed family, also known as Lemnaceae family. These rapidly growing plants have found uses as a model system for studies in basic plant biology, in eco-toxicology, in production of biopharmaceuticals, and as a source of animal feeds for agriculture and aquaculture.
Lemna species grow as simple free-floating thalli on or just beneath the water surface. Most are small, not exceeding 5 mm in length, except Lemna trisulca which is elongated and has a branched structure. Lemna thalli have a single root. The plants grow mainly by vegetative reproduction. This form of growth can allow very rapid colonization of new water.
The rapid growth of duckweeds finds application in bioremediation of polluted waters and as test organisms for environmental studies. It is also being used as an expression system for economical production of complex biopharmaceuticals.
Dried duckweed can be a good cattle feed. It can contain 25-45% protein (depending on the growth conditions), 4.4% fat, and 8-10% fiber, measured by dry weight.
Duckweed can be farmed organically, with nutrients being supplied from a variety of sources, for example cattle dung, pig waste, biogas plant slurry, or other organic matter in slurry form.